Adjustable latching mechanism

ABSTRACT

The adjustable latching mechanism functions on the vernier principle. In the preferred embodiment, a row of pivotally mounted side-by-side detent elements corresponds to a vernier scale. A latching element having a plurality of recesses corresponds to the regular measuring scale. The latching element is movable with respect to the detent elements. The detent elements are biased towards engagement with the recesses. At any given relative position of the detent elements and latching element, one of the detent elements will always be close to or in alignment with one of the recesses in accordance with the vernier principle for pivotal movement thereinto to result in locking engagement.

United States Patent Bracey 1 Feb. 6, 1973 41 ADJUSTABLE LATCHING Primary Examinerl\/lilton Kaufman MECHANISM Attorney-Whittemore, Hulbert & Belknap [76] lnventor: Robert A. Bracey, 4628 Johnathan,

Dearborn, Mich. 48126 [57] ABSTRACT Filed: June151971 The ad ustable latching mechanism functions on the Appl. No.: 153,242

as J /0 a4 40 Z vernier principle. In the preferred embodiment, a row of pivotally mounted side-by-side detent elements corresponds to a vernier scale. A latching element having a plurality of recesses corresponds to the regular measuring scale. The latching element is movable with respect to the detent elements. The detent elements are biased towards engagement with the recesses. At any given relative position of the detent elements and latching element, one of the detent elements will always be close to or in alignment with one of the recesses in accordance with the vernier principle for pivotal movement thereinto to result in locking engagement.

17 Claims, 12 Drawing Figures ADJUSTABLE LATCHING MECHANISM BACKGROUND OF THE INVENTION Adjustable latching mechanisms of the general type in which it is desired to latch one member at different locations along another member have been proposed in the past. Such latching mechanisms have primarily been based either on frictional engagement principles or positive mechanical interlocking principles. The frictional engagement type of latching mechanism possesses the advantage of infinite adjustment of one member with respect to another. However, all frictional systems have one basic disadvantage in that the use of friction as the engaging force always involves the danger of slippage because of the inherent nature of friction. The use of mechanical interlocking devices results in desired positive latching. However, the bulkiness of interlocking mechanical devices has resulted in permitting latching at discrete points which are spaced apart from each other by relatively large increments. For example, one type of latching involves providing opposed teeth on the two members. The points of latching are thus spaced apart a distance equal to the width of one tooth. When smaller teeth are provided to decrease this distance, the holding strength of the latching mechanism is undesirably reduced.

In accordance with the present invention, an adjustable latching device is provided in which positive engagement of interlocking mechanical parts is utilized, thus overcoming the disadvantages of frictional latching. The device involves the use of interlocking recesses and detents which are related to each other in accordance with the vernier principle. This results in the points of latching being spaced apart by very small distances. However, the interlocking parts may be of relatively heavy construction to thereby provide desired strength characteristics. Manufacture of the device does not necessarily involve close tolerances and therefore the device may be manufactured at a relatively low cost. The latching mechanism may be adapted to numerous different environments to thereby solve many different types of latching problems.

SUMMARY OF THE INVENTION T2 adjustable latching mechanism comprises a plurality of detent elements which are pivotally mounted tent elements or the number of recesses per said unit length is not a whole number multiple of the other. The row of detent elements and the latching element are relatively movable with respect to each other with the detent elements facing the recesses whereby at any given position one of the detent elements will always be close to or in alignment with one of the recesses in accordance with the vernier principle for pivotal movement thereinto to result in locking engagement. Preferably, the row of detent elements is shorter than the row of recesses and defines the unit length. Also, preferably there are more detent elements'per unit length than there are recesses.

IN THE DRAWINGS FIG. I is a side elevational view partially in section of one embodiment the adjustable latching mechanism of the present invention;

FIG. 2 is a side elevational view of the adjustable latching mechanism of FIG. 1 illustrated in the unlatched condition;

FIG. 3 is a sectional view taken substantially along the line 3-3 of FIG. 1 looking in the direction of the arrows;

FIG. 4 is a sectional view taken substantially along the line 4-4 of FIG. 2 looking in the direction of the arrows;

FIG. 5 is a view in perspective of another embodiment of the adjustable latching mechanism of the present invention;

6 is a front elevational view of another embodiment of the invention with portions broken away for the purpose of clarity;

FIG. 7 is an exploded view in perspective of another embodiment of the adjustable latching mechanism of the invention;

FIG. 8 is a cross sectional view of the adjustable latching mechanism of FIG. 7 shown in the assembled condition and in the latched position;

FIG. 9 is a view of the adjustable latching mechanism similar to FIG. 8 illustrating the unlatched position;

FIG. 10 is front elevational view of a rotary adjustable latching mechanism forming another embodiment of the invention;

FIG. 11 is a sectional view taken substantially along the line ll1l of FIG. 10 looking in the direction of the arrows; and

FIG. 12 is a view of the upper portion of the FIG. 11 sectional view illustrating the mechanism in the unlatched condition.

Referring first to the embodiment of the adjustable mechanism illustrated in FIGS. 1-4, it will be noted that the mechanism 10 includes an elongated latching element 12 which is slidably received in an axially extending-opening 18 provided through a cylindrical casing member 20. The ends of the casing member 20 are received in recesses provided in spaced apart upstanding post elements 14, 16 which thereby support the easing. The casing is maintained in position and against rotation by means of set screws 22, 24. The post elements are supported by means of a base plate 26. Enlarged openings 28, 30 are provided in the post elements l4, 16 in alignment with the opening 18 to permit free passage of the latching element 12.

The latching element 12 is a cylindrical element. A plurality of spaced apart recesses 32 are provided in alignment to form a row on one side of the element 12. Each recess 32 comprises a first radially extending surface 34. The surface 34 extends to a depth equal to about one-third the diameter of the element 12. An axially directed bottom surface 36 extends from the surface 34. An inclined surface 38 extends from the bottom surface 36 back to the outer periphery of the element 12. Each recess is spaced from the adjacent recess a distance equal to the length of peripheral surface portion 40. A handle element 42 is provided in the outer end of the element 12 to facilitate manual rotation of the element 12.

A portion of the wall of the casing 20 is cut away between the posts l4, 16. The cut away portion defines an opening 44 for ingress of a plurality of detents 46 to permit engagement of the detents with the recesses 32 of the latching element 12. The opening 44 extends around the casing for approximately two-thirds of the periphery thereof. The detents 46 are mounted in side-by-side stacked relationship in a row between the ends of the opening 44 by means of an axle 48 which extends through aligned openings provided in the detents and in the casing. The detents are pivotable on the axle 48.

As will be noted in FIGS. 3 and 4, each detent 46 is generally semi-circular in exterior configuration, the radius of each detent being substantially equal to the radius of the casing 20. An ear 50, 52 extends circumferentially from each diametric side of each detent. One ear 50 has an opening therein for reception of the axle 48. The other ear is free to move. The two ears define a central recess 56 in each detent.

A spring element 58 extends between the posts 14, 16 and is secured thereto by means of screws 60, 62, which also extend through a support plate 63. The spring element 58 has a plurality of spaced apart spring fingers 64 each of which extends therefrom into engagement with the exterior peripheral surface of one of the detents 46, constantly urging the detents in the clockwise direction as viewed in FIGS. 3 and 4.

In operation of the structure thus described, one of the detents 46' (FIGS. 1 and 3) is adapted to be biased nearly or completely into one of the recesses 32 whenever the latching element 12 is rotated to the position illustrated in FIG. 1 wherein the mouths of the recesses face the detents. In addition to the one detent which is illustratively completedly received in a recess, it will be noted that others of the detents are partially inserted into opposed recesses. Only those detents which contact the s portion 40 between the recesses are completely out ofthe recesses.

The width of the detents, as for example detent 46', is slightly greater than the width of the recess bottom surfaces 36. This is to prevent jamming of the detents in the recesses.

It will be appreciated from a view of FIG. 1, that once a radial surface 34 is contacted by a detent 46, the

' latching element 12 is positively prevented from movement to the right as viewed in FIG. 1. However, the latching element 12 may be shifted to the left because the inclined surfaces 38 act as camming surfaces and cam the detents out of the way upon leftward movement. When it is desired to adjust the latching element 12 to the right, it is only necessary to pivot it 90 by use of the handle element 42 whereupon, as will be noted in FIGS. 2 and 4, the recesses are moved out of alignment with the detents and the latching element 12 is freely slidable in either direction.

The device is broadly based on the vernier principle so that relatively fine adjustments of the position of the latching element 12 may be made even though the detents 46 and recesses 32 are relatively wide. As is well known, the vernier principle is used in scaling. Basically, a short scale termed the vernier is made to slide along the divisions of a graduated instrument for indicating parts of divisions and is so graduated that a convenient number of its divisions are just equal in length to a number (either one less or one more) of the divisions of the instrument and so that parts of a division are determined by observing what line on the vernier coincides with the line on the instrument.

In the present case, instead of coinciding lines, there are coinciding detents and recesses which result in the desired latching action. In the embodiment illustrated, there are 12 detents 46 in a row which row matches in length a row of five recesses 32. The row of detents defines a unit length for the vernier. As will be appreciated, the more detents there are with respect to the number of recesses, the finer will be the adjustment. However, it has been found that with the relatively large size of the detents and recesses illustrated, wherein a working model was provided with detents 0.2242 inch wide, and recesses having an overall width from recess to recess of 0.5500 inch, that a detent will engage a recess every 0.0458 inch. Movement equal to the overall width of one recess results in 12 different detents engaging a recess.

Normally a vernier scale would have, as above stated, one more or one less division than the scale with which it is used. However, as will be noted in the present case, there are seven more detents than there are recesses. The more detents that are present, the finer will be the adjustment. A true vernier arrangement is not practical because of size limitation. In deciding the number of detents or recesses to be used, it is only necessary that the number of detents not be a whole number multiple of the number of recesses or vice-versa. If a multiple were used, then engagement will occur when the device was moved a distance equal to the width of one detent or one recess as the case may be. The fine adjustment available with the device illustrated would not be possible.

A modified version of the invention is illustrated in FIG. 5. The adjustable latching mechanism 66 includes a block 68 having a central opening therethrough through which slidably extends a bar 70. The bar 70 has a plurality of spaced apart openings 72. Four spaced apart openings 78 are provided in the block 68. The distance between six of the openings 72 equals the distance between the four openings 78 so that again, the vernier principle is employed with respect to alignment of the openings 72, 78. One pair of the openings is always in relatively close alignment. The block 68 may thus be secured along the bar 70 substantially in any desired location. The bar 70 is supported and guided through an opening provided in a post 80. The bar 70 may be slid to any desired position, either manually or power operated, whereupon the block 68 is secured thereto by means of a pin 82 manually inserted through the most closely aligned openings 72, 78.

The block 68 is provided with a plurality of recesses 84 in the upper portion thereof. The sidewalls of the recesses 84 are upright for positive engagement with one detent 86 of the stack 88 of detents which is positioned above the block 68. Representatively, there are ten detents 86 which define a row of unit length equal to six of the seven recesses 84. The detents 86 are pivotally mounted on an axle 90 carried by a housing 92. A spring structure 94 having a plurality of spring fingers 95 each of which engages a detent 86 is provided to bias the detents downwardly towards the recesses 84.

The housing 92 has a pair of upstanding guide posts 96, 98 which extend through openings provided in support and guide structures 100, 102. The structures 100, 102 are fixedly mounted on support structure 104. The stack 88 of detents 86 may be raised and lowered, either manually or by power means, into engagement with the recesses 84 of the block 68. As previously described, one of the detents will likely engage or be in very close engagement with one of the recesses. It is possible with this device to normally so position the block 68 as to insure that one of the detents will directly engage one of the recesses. In this manner, it is possible to accurately locate the position of the bar 70 wherever desired.

FIG. 6 illustrates an embodiment similar in construction to the FIG. 1 embodiment. The adjustable latching mechanism 106 includes an elongated latching element 108 having recesses 118 slidingly received in a casing member 110 in which is pivotally mounted a row of side-by-side detents 112. The casing member 110 is supported on posts 1 14, 116 as previously described.

Instead of mechanically biasing the detents 112 into the recesses 118 as by means of a spring structure, a housing 122 is provided around the detents. The housing 122 is secured to the casing 110 by means of screws 124. The attachment of the housing 122 to the casing 110 is not made fluid tight but rather has fluid leaks between the screws 124. A hose 126 is secured to the housing 122 by means of a fitting 128. The outlet of the hose is in communication with the interior of the chamber 130. The hose is connected at the other end to a suitable source of air under pressure 132.

In operation of the mechanism 106, the latching element 108 is manipulated as described in connection with the FIG. 1 embodiment. When it is desired to engage the latching element with a detent 112, a valve 134 is opened thus providing air under pressure in the chamber 130 causing the detents to be biased towards the recesses 118. One of the detents will be received in one of the recesses. The air pressure will cause slight shifting of the latching element in the'event that the detent is not in exact alignment with a recess. This results from the camming action of the detents against inclined surfaces 136. The air pressure created in the chamber 130 is allowed to escape via the leaks between the screws 124 so that the chamber 130 is not maintained at an elevated pressure and to provide a low pressure zone on the reverse side of the detents to improve the pressure biasing action as a result of air flow. Air flow may be maintained to hold the detents in place although gravity will function for this purpose with the device oriented as shown. The detents are released by rotating element 108.

Another embodiment of an adjustable latching mechanism 138 is illustrated in FIGS. 79. FIG. 7 is an exploded view of the various components of the latching mechanism. The components include an elongated latching bar 140 which is generally rectangular in cross-section. A plurality of recesses 146 of the general configuration of the recesses 32 in the FIG. 1 embodiment are provided on the upper portion of the bar 140.

The latching bar 140 is slidably received in an elongated recess 148 provided in a housing 150. The housing 150 has a back wall comprising first upright portion 152, second rearwardly angled portion 154 and third forwardly angled portion 156. An elongate recess 158 is provided in the portion 156. The recess 158 defines a pair of ears 160, 162 in which openings are provided. The axle 164 of a row 166 of detents 168 is journaled in the openings provided in the ears 160, 162. An elongated slot 170 is provided beneath the recess 158 to receive an elongated camming member 172 which extends at an angle from manually engageable support wall 174. The camming member 172 is of a size to be received in the slot 170. A spring structure 176 including spaced apart spring fingers 178 is secured to the wall portion 156 with the fingers 178 extending into engagement with the upper surfaces of the detents 168.

FIGS. 8 and 9 illustrate the assembled device in both the latched and unlatched condition. As will be noted in FIG. 8, one of the detents 168 is in engagement with a recess 146, being biased into such engagement by means of the spring finger 178. When it is desired to unlatch the device and move the latching bar 140, the camming member 172 is inserted through the slot 170 to cammingly engage the rear edge of the detents 168 and pivot these detents out of engagement with the recesses of latching bar 140 against the action of the spring structure 176. The bar 140 may then be slid in the recess 148 to any desired position whereupon the camming member 172 is removed permitting re-engagement of a detent 168 with a recess 146.

FIGS. 10-12 illustrate a rotary adjustable latching mechanism 180. The latching mechanism 180 includes an annular latching disc 182 which is journaled on an axle 184 by means of a bushing 186 for rotation thereabout. The disc 182 has a plurality of spaced apart recesses 188 around the outer periphery thereof. The recesses 188 have a configuration similar to the recesses 32 of FIG. 1 including an inclined surface 190. A crank handle 192 is provided on the disc 182 to permit the manual manipulation of the disc.

A second annular disc 194 is provided adjacent the disc 182. The disc 194 is fixedly mounted on the axle 184 by means of a key 196. The disc 194 supports and positions a detent structure 198. Additionally, the disc 194 acts as a reinforcement for the disc 182. j

The detent structure 198 includes a curved support member 200 which extends radially outwardly from the upper edge of the disc 194. A plurality of radially extending recesses 202 are provided in the member 200. The mouths of the recesses 202 face the recesses 188 of the latching disc 182. The recesses 202 are separated bywall portions 204.

A detent 206 is pivotally mounted in each recess 202. The detents 206 cannot be stacked directly adjacent as in the previously described embodiments because when the detents pivot each detent will follow a slightly different angular path than the adjacent detent. It would cause interference if the detents were directly adjacent each other. However, they are arranged in a curved row in side-by-side fashion. As will be noted in FIGS. 11 and 12, each detent has a circular portion 208 on its inner end which is received in a circular recess 210 provided in each of the recesses 202. The remaining portion of each detent is curved in a direction generally towards the recesses provided in the latching disc 182. The recesses 202 are relieved above the detents 206 to permit retraction of the detents as illustrated in FIG. 12.

The detents are not provided with a spring or other biasing element to urge them into the recesses 202-The detents fall into the recesses as a result of gravity. For this reason, the detents must be located above the latching recesses. A pin 214 extends from each detent. All of the detents may be retracted to disengage the latching disc 182 by means of the manual cam element 216 which is curved in the 'same shape as the support member 200. However, the detents need not be disengaged in order to adjust the latching disc 182, the latching disc 182 being movable in the counterclockwise direction as viewed in FIG. 10 as a consequence of the inclined surfaces 190 which will cam the detents out of engagement as the latching disc is rotated in the counterclockwise direction. Because of thecircular nature of the latching disc, any position of the disc desired may be achieved by rotation thereof.

What I claim as my invention is:

1. An adjustable latching mechanism comprising a plurality of detent elements mounting means for said detent elements, said detent elements being pivotally mounted in said mounting means in side-by-side relationship in a row, a latching element having a plurality of recesses arranged in side-by-side relationship in a row, one of said rows being shorter than-the other and defining a unit length, there being a difference of at least one between the number of detents and the number of recesses per said unit length, one of the number of detent elements or the number of recesses per said unit length not being a whole number multiple of the other, said row of detent elements and said latching element being relatively movable with respect to each other with the detent elements facing the recesses whereby at any given position one of the detent elementswill always be close to or in alignment with one of the recesses in accordance with the vernier principle for pivotal movement 'thereinto to result in locking engagement.

2. A mechanism as defined in claim 1, further characterized in that said row of recesses is longer than said row of detent elements.

3. A mechanism as defined in claim 2, further characterized in that said latching element has a curved portion on the side opposite from said recesses, means mounting said latching element for sliding parallel to the row of detent elements and for rotation about an axis parallel thereto whereby the latching element may be disengaged from said detent elements by rotation thereof to present the curved portion thereof to the detent elements.

4. A mechanism as defined in claim 1, further characterized in that said rows are linear.

5. A mechanism as defined in claim 1, further characterized in that said rows are configured along circular paths.

6. A mechanism as defined in claim 1, further characterized in that there are more detent elements per said unit length than there are recesses.

7. A mechanism as defined in claim 6, further characterized in that there are more than twice as many detent elements per unit length as there are recesses.

8. A mechanism as defined in claim 1, further characterized in the provision of means to bias each of the detent elements towards the recesses.

9. A mechanism as defined in claim 8, further characterized in that said means to bias the detent elements comprises aspring secured to said mounting means and having a plurality of spring fingers, each spring finger being in engagement with one of the detent elements to bias said elements towards the recesses.

10. A mechanism as defined in claim 8, further characterized in that said means to bias comprises chamber means provided over said detent elements, an inlet to said chamber means, a source of air under pressure, means connecting said inlet to said source of air under pressure for injecting air under pressure into the chamber means, and outlet means for flow of air through the chamber in a direction to apply pressure to the detent elements biasing the elements towards the recesses.

11. A mechanism as defined in claim 8, further characterized in that said detent elements are positioned above said recesses whereby to be biased towards the recesses as a consequence of gravity.

12. A mechanism as defined in claim 1, further characterized in the provision of a cam structure equal in length to the length of the row of detent elements, said cam structure being engageable with the detent elements to pivot the elements out of engagement with the latching element.

13. A mechanism as defined in claim 1, further characterized in the provision of means connected to the mounting means for the detent elements for moving said detent elements in a path towards and away from the latching element to permit selective engagement and disengagement of the detent elements with the latching element.

14. A mechanism as defined in claim 1, further characterized in that said recesses each have one sidewall inclined at an obtuse angle to the pivotal axis of the detent elements, each of said recesses having an opposed wall oriented at substantially right angles to the pivotal axis of the detent elements whereby a detent element received in a recess will prevent relative movement in one direction but will be cammed out of the recess upon movement in the opposite direction.

15. A mechanism as defined in claim 1, further characterized in that said recesses have opposed sidewalls which are oriented at substantially right angles to the pivotal pivotal axis of the detent elements whereby-reception of a detent element in a recess will prevent relative movement of the latching element and detent elements.

16. A mechanism as defined in claim 1, further characterized in that said latching element is annular, said recesses being provided in annular row thereon, said detent elements arranged in a mating annular row.

17. An adjustable latching mechanism comprising a plurality of detent elements, mounting means for said detent elements, said detent elements being pivotally mounted in said mounting means in side-by-side relationship in a row defining an arbitrary unit length, the latching element having a plurality of recesses arranged in side-by-side relationship in a row of greater length than said unit length there being a difference of a least one between the number of detents and the number of recesses per said unit length, the number of detent elements per said unit length not being a whole number multiple of the number of recesses per said unit length, said latching element being movable with respect to the row of detent elements with the detentelements facing 

1. An adjustable latching mechanism comprising a plurality of detent elements mounting means for said detent elements, said detent elements being pivotally mounted in said mounting means in side-by-side relationship in a row, a latching element having a plurality of recesses arranged in side-by-side relationship in a row, one of said rows being shorter than the other and defining a unit length, there being a difference of at least one between the number of detents and the number of recesses per said unit length, one of the number of detent elements or the number of recesses per said unit length not being a whole number multiple of the other, said row of detent elements and said latching element being relatively movable with respect to each other with the detent elements facing the recesses whereby at any given position one of the detent elements will always be close to or in alignment with one of the recesses in accordance with the vernier principle for pivotal movement thereinto to result in locking engagement.
 1. An adjustable latching mechanism comprising a plurality of detent elements mounting means for said detent elements, said detent elements being pivotally mounted in said mounting means in side-by-side relationship in a row, a latching element having a plurality of recesses arranged in side-by-side relationship in a row, one of said rows being shorter than the other and defining a unit length, there being a difference of at least one between the number of detents and the number of recesses per said unit length, one of the number of detent elements or the number of recesses per said unit length not being a whole number multiple of the other, said row of detent elements and said latching element being relatively movable with respect to each other with the detent elements facing the recesses whereby at any given position one of the detent elements will always be close to or in alignment with one of the recesses in accordance with the vernier principle for pivotal movement thereinto to result in locking engagement.
 2. A mechanism as defined in claim 1, further characterized in that said row of recesses is longer than said row of detent elements.
 3. A mechanism as defined in claim 2, further characterized in that said latching element has a curved portion on the side opposite from said recesses, means mounting said latching element for sliding parallel to the row of detent elements and for rotation about an axis parallel thereto whereby the latching element may be disengaged from said detent elements by rotation thereof to present the curved portion thereof to the detent elements.
 4. A mechanism as defined in claim 1, further characterized in that said rows are linear.
 5. A mechanism as defined in claim 1, further characterized in that said rows are configured along circular paths.
 6. A meChanism as defined in claim 1, further characterized in that there are more detent elements per said unit length than there are recesses.
 7. A mechanism as defined in claim 6, further characterized in that there are more than twice as many detent elements per unit length as there are recesses.
 8. A mechanism as defined in claim 1, further characterized in the provision of means to bias each of the detent elements towards the recesses.
 9. A mechanism as defined in claim 8, further characterized in that said means to bias the detent elements comprises a spring secured to said mounting means and having a plurality of spring fingers, each spring finger being in engagement with one of the detent elements to bias said elements towards the recesses.
 10. A mechanism as defined in claim 8, further characterized in that said means to bias comprises chamber means provided over said detent elements, an inlet to said chamber means, a source of air under pressure, means connecting said inlet to said source of air under pressure for injecting air under pressure into the chamber means, and outlet means for flow of air through the chamber in a direction to apply pressure to the detent elements biasing the elements towards the recesses.
 11. A mechanism as defined in claim 8, further characterized in that said detent elements are positioned above said recesses whereby to be biased towards the recesses as a consequence of gravity.
 12. A mechanism as defined in claim 1, further characterized in the provision of a cam structure equal in length to the length of the row of detent elements, said cam structure being engageable with the detent elements to pivot the elements out of engagement with the latching element.
 13. A mechanism as defined in claim 1, further characterized in the provision of means connected to the mounting means for the detent elements for moving said detent elements in a path towards and away from the latching element to permit selective engagement and disengagement of the detent elements with the latching element.
 14. A mechanism as defined in claim 1, further characterized in that said recesses each have one sidewall inclined at an obtuse angle to the pivotal axis of the detent elements, each of said recesses having an opposed wall oriented at substantially right angles to the pivotal axis of the detent elements whereby a detent element received in a recess will prevent relative movement in one direction but will be cammed out of the recess upon movement in the opposite direction.
 15. A mechanism as defined in claim 1, further characterized in that said recesses have opposed sidewalls which are oriented at substantially right angles to the pivotal pivotal axis of the detent elements whereby reception of a detent element in a recess will prevent relative movement of the latching element and detent elements.
 16. A mechanism as defined in claim 1, further characterized in that said latching element is annular, said recesses being provided in annular row thereon, said detent elements arranged in a mating annular row. 